U.S. patent number 8,464,811 [Application Number 12/808,519] was granted by the patent office on 2013-06-18 for steerable system.
This patent grant is currently assigned to Schlumberger Technology Corporation. The grantee listed for this patent is Michael Shepherd. Invention is credited to Michael Shepherd.
United States Patent |
8,464,811 |
Shepherd |
June 18, 2013 |
Steerable system
Abstract
A steerable system comprises a first rotatable housing and a
second rotatable housing connected to the first rotatable housing
by an adjustable joint. A cam member is held against rotation while
in use. Cam follower means are cooperable with the cam member and
moveable to drive the second rotatable housing for movement
relative to the first rotatable housing about the adjustable
joint.
Inventors: |
Shepherd; Michael (Glos,
GB) |
Applicant: |
Name |
City |
State |
Country |
Type |
Shepherd; Michael |
Glos |
N/A |
GB |
|
|
Assignee: |
Schlumberger Technology
Corporation (Sugar Land, TX)
|
Family
ID: |
39048310 |
Appl.
No.: |
12/808,519 |
Filed: |
December 19, 2008 |
PCT
Filed: |
December 19, 2008 |
PCT No.: |
PCT/IB2008/003950 |
371(c)(1),(2),(4) Date: |
October 29, 2010 |
PCT
Pub. No.: |
WO2009/101477 |
PCT
Pub. Date: |
August 20, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110100716 A1 |
May 5, 2011 |
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Foreign Application Priority Data
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Dec 19, 2007 [GB] |
|
|
0724699.4 |
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Current U.S.
Class: |
175/73 |
Current CPC
Class: |
A61F
13/15747 (20130101); B65H 29/62 (20130101); E21B
7/06 (20130101); E21B 7/067 (20130101); E21B
7/062 (20130101); B65H 29/60 (20130101) |
Current International
Class: |
E21B
7/04 (20060101) |
Field of
Search: |
;175/61,73,74,82,83 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2368361 |
|
May 2002 |
|
GB |
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01/46549 |
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Jun 2001 |
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WO |
|
Primary Examiner: Stephenson; Daniel P
Assistant Examiner: Wills, III; Michael
Attorney, Agent or Firm: Sullivan; Chadwick A.
Claims
The invention claimed is:
1. A steerable system comprising a first rotatable housing, a
second rotatable housing connected to the first rotatable housing
by an adjustable joint, a cam member held against rotation, in use,
and a cam follower cooperable with the cam member, the cam follower
comprising follower pistons which are reciprocable in corresponding
bores, the follower pistons causing movement of associated drive
members in a manner which provides mechanical advantage enabling
the associated drive members to apply a larger force, the
associated drive members being moveable to drive the second
rotatable housing for movement relative to the first rotatable
housing about the adjustable joint.
2. A system according to claim 1, wherein the first and second
rotatable housings are connected to one another in such a manner
that rotation of the first housing is transmitted to the second
housing.
3. A system according to claim 2, further comprising a clutch
mechanism operable to allow rotation of the first housing relative
to the second housing.
4. A system according to claim 3, wherein the clutch mechanism
comprises a dog clutch.
5. A system according to claim 1, wherein the cam member is
adjustable to permit adjustment of the orientation of the second
housing.
6. A system according to claim 1, wherein the cam member is mounted
to a sleeve which surrounds at least part of the first housing and
which is held against rotation in normal use.
7. A system according to claim 6, wherein the sleeve comprises a
stabiliser.
8. A system according to claim 6, wherein a spherical bearing is
provided and arranged to support the cam member relative to the
sleeve.
9. A system according to claim 6, wherein one or more linear
actuators are provided to drive the cam member for movement
relative to the sleeve to adjust its position.
10. A system according to claim 9, wherein the or each linear
actuator is electrically driven, electromagnetically driven or is
hydraulically powered.
11. A system according to claim 6, wherein the cam member is in the
form of a swash plate.
12. A system according to claim 1, wherein the cam followers
comprise follower pistons arranged to be driven by the cam member
and moveable to cause movement of drive pistons.
13. A system according to claim 12, wherein the follower pistons
are of smaller diameter than the drive pistons so as to provide a
mechanical advantage.
14. A system according to claim 12, wherein movement of the drive
pistons is transmitted to the second housing by associated push
rods.
15. A system according to claim 14, wherein the push rods are
aligned with the corresponding ones of the follower pistons.
16. A system according to claim 1, wherein the associated drive
members comprise associated drive pistons.
17. A system according to claim 1, wherein the cam member is
mounted to a sleeve which surrounds at least part of the first
housing and which is held against rotation in normal use.
18. A system according to claim 17, wherein the sleeve comprises a
stabiliser.
19. A system according to claim 18, further comprising a spherical
bearing positioned to support the cam member relative to the
sleeve.
20. A system according to claim 19, further comprising linear
actuators oriented to drive the cam member for movement relative to
the sleeve to adjust its position.
21. A system according to claim 16, wherein the associated drive
pistons have larger diameters than the follower pistons such that
each associated drive piston is moved over a smaller distance than
the corresponding follower piston when acted on by the
corresponding follower piston to provide the mechanical advantage.
Description
FIELD OF INVENTION
This invention relates to a steerable system, for example for use
in the formation of boreholes.
BACKGROUND
It is commonplace in the field of borehole formation, for
subsequent use in the extraction of hydrocarbons, to use a
steerable drilling system to allow control over the path of the
borehole. A number of steerable drilling systems are known. For
example systems are known in which a bias unit is located close to
the drill bit, the bias unit being operable to apply a laterally
directed load to the drill bit urging it away from the axis of the
borehole in a desired direction. Another form of steerable drilling
system includes a bent housing upon which the drill bit is mounted,
steering of the system being achieved by controlling the
orientation of the bent housing to ensure that the drill bit is
pointed in a desired direction. In some arrangements the bent
housing is adjustable to control the direction and angle of the
drill bit. In other arrangements, the bent housing is of fixed
inclination and adjustment of the direction in which the drill bit
is pointed is achieved by controlling the angular position of the
bent housing.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a steerable system of
simple and convenient form.
According to the present invention there is provided a steerable
system comprising a first rotatable housing, a second rotatable
housing connected to the first rotatable housing by an adjustable
joint, a cam member held against rotation, in use, and cam follower
means cooperable with the cam member and moveable to drive the
second rotatable housing for movement relative to the first
rotatable housing about the adjustable joint.
Such an arrangement is advantageous in that the axis of rotation of
the second rotatable housing can be held in a substantially fixed
position whilst the first and second rotatable housings are
rotated. A drill bit carried by the second housing can thus be held
in a desired orientation whilst drilling takes place.
Preferably, the first and second rotatable housings are connected
to one another in such a manner that rotation of the first housing
is transmitted to the second housing. A clutch mechanism, for
example in the form of a dog clutch, may be provided to allow
rotation of the first housing relative to the second housing.
The cam member is conveniently adjustable to permit adjustment of
the orientation of the second housing. The cam member is
conveniently in the form of a swash plate. The cam member is
preferably mounted to a sleeve which surrounds at least part of the
first housing and which is held against rotation in normal use. For
example, the sleeve may comprise a stabiliser. A spherical bearing
is preferably provided on the first housing and arranged to support
the cam member. One or more linear actuators are preferably
provided to drive the cam member for movement relative to the
sleeve to adjust its position. The or each linear actuator may be
electrically driven or, alternatively, may be hydraulically
powered.
The cam followers means preferably comprise follower pistons
arranged to be driven by the cam member and moveable to cause
movement of drive pistons. The follower pistons are conveniently of
smaller diameter than the drive pistons so as to provide a
mechanical advantage. Movement of the drive pistons is conveniently
transmitted to the second housing by associated push rods.
The push rods are conveniently aligned with the corresponding ones
of the follower pistons. In such an arrangement the second housing
will be inclined relative to the first housing in the same
direction as the cam member, but the angle of inclination will be
smaller.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will further be described, by way of example, with
reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic view of a steerable drilling system
incorporating the steerable system of one embodiment of the
invention; and
FIG. 2 is an enlarged, sectional view illustrating the steerable
system of the drilling system of FIG. 1.
DETAILED DESCRIPTION
Referring to the accompanying drawings there is illustrated a
steerable drilling system being used in the formation of a
borehole. The steerable drilling system comprises a drill string 10
supporting a number of downhole components. The drill string 10 is
supported, at the surface, by a rig which serves both a supporting
function and also drives the drill string 10 for rotation.
The drill string 10 carries a number of intermediate stabiliser
units 12 and, at its lower end, carries a bottom hole assembly 14.
The bottom hole assembly 14 includes a downhole motor 16, a
steerable system 18, and a drill bit 20. In use, the motor 16
serves to drive the drill bit 20 for rotation. The rotation of the
drill bit 20, in combination with weight on bit loadings applied
thereto, causes the drill bit 20 to gauge, scrape or abrade
material from the formation in which the borehole is being formed,
extending the borehole.
Although the arrangement illustrated makes use of a downhole motor,
arrangements are also possible in which the drill bit is driven by
the rotation of the drill string.
The steerable system 18 operates to ensure that, whilst drilling is
taking place, the drill bit 20 is held in a desired orientation,
thus controlling the direction in which the borehole is
extended.
As best illustrated in FIG. 2, the steerable system 18 comprises a
first rotatable housing 22 arranged to be connected to the output
of the downhole motor 16 so as to be driven for rotation thereby. A
second rotatable housing 24 is connected to the first housing 22 by
an adjustable joint 26, for example in the form of a universal
joint or swivel. The joint 26 includes a part spherical thrust
bearing 28 thus permitting the transmission of axially directed
loadings from the first housing 22 to the second housing 24, whilst
permitting the angle of the axis 24a of the second housing 24 to be
adjusted relative to that of the first housing 22.
A releasable torque transmission arrangement in the form of a dog
clutch 30 is provided between the first and second housings 22, 24
such that, when desired, rotation of the first housing 22 about its
axis can be transmitted to the second housing 24, release of the
dog clutch 30 permitting the first housing 22 to rotate
independently of the second housing 24.
An axially extending passage 32 extends through the first housing
22 and the joint 26 to a passage 34 provided in the second housing
24, thus permitting drilling fluid or mud to be supplied through
the steerable system 18.
A stabiliser sleeve 36 surrounds part of the first housing 22. The
sleeve 36 bears against the wall of the borehole and remains
substantially fixed against rotation, in use. The sleeve 36 is
mounted to the first housing 22 by bearings 38, which also serve as
seals, so as to allow the first housing 22 to rotate whilst the
sleeve 36 remains fixed against rotation. The sleeve 36 and first
housing 22 together define a chamber 40 within which a cam member
in the form of a swash plate 42 is located. The swash plate 42 is
keyed or splined to the sleeve 36 such that, in normal use, it is
held against rotation. The nature of the connection between the
swash plate 42 and the sleeve 36 is such that the angular
orientation of the swash plate 42 can be adjusted. A spherical
bearing 44 is provided between the inner part of the swash plate 42
and the adjacent part of the first housing 22 to accommodate such
movement whilst supporting the swash plate 42. A series of linear
actuators 46 are mounted upon the sleeve 36 and engage the swash
plate 42, the linear actuators 46 being operable under the control
of an appropriate control system (not shown) to adjust the
orientation of the swash plate 42 relative to the sleeve 36. The
linear actuators 46 may take a range of forms. For example, they
could be electrically or electromagnetically actuated, or
alternatively they may be hydraulically operated.
The opposite face of the swash plate 42 to that which cooperates
with the linear actuators 46 engages a series of cam follower means
48. The cam follower means 48 each comprises a relatively small
diameter follower piston 50 which bears against the swash plate 42
and which is reciprocable within a corresponding bore 52 formed in
the first housing 22. The bore 52 opens into a larger diameter bore
54 in which a larger diameter drive piston 56 is reciprocable. It
will be appreciated that, with such an arrangement, movement of the
follower piston 50 causes movement of the associated drive piston
56 in the same direction. The drive piston 56 will move through a
smaller distance than the follower piston 50, but is able to apply
a larger force by virtue of the mechanical advantage so gained.
A series of push rods 58 bear against the drive pistons 56,
transmitting movement thereof to the second housing 24.
In use, in the position illustrated in FIG. 2 it will be
appreciated that the swash plate 42 is angled relative to the first
housing 22, and that the second housing 24 is tilted relative to
the first housing 22 in the same direction as the swash plate 42
but by a smaller angle. From this position, rotation of the first
housing 22 due to the operation of the motor 16 causes the follower
pistons 50, in turn, to ride up and over the swash plate 42, the
follower pistons 50 each being pushed further into the
corresponding bores 52 by their movement over the swash plate 42.
The movement of the follower pistons 50 is transmitted, by the
fluid within the bores 52, 54, to the associated drive pistons 56,
extending the push rods 58 and urging the second housing 24 to tilt
about the joint 26. The tilting movement of the second housing 24
so achieved drives the push rods 58, and drive and follower pistons
56, 50 on the radially opposite side of the steerable system in the
reverse direction towards a retracted position. It will be
appreciated that this action ensures that the axis of rotation 24a
of the second housing 24 is held substantially fixed in space
whilst the first and second housings 22, 24 are rotated.
Consequently, the drill bit 20 is held in a desired orientation
whilst drilling takes place.
Appropriate adjustment of the position of the swash plate 42 by the
linear actuators 46 can be used to adjust the degree of inclination
of the second housing 24 relative to the first housing 22 and to
adjust the direction or orientation of the axis of rotation 24a of
the second housing 24 relative to the first housing 22. It will
thus be appreciated that, by appropriate control of the position of
the swash plate 42 using the linear actuators 46, the direction of
drilling of the steerable drilling system can be controlled.
The mechanical advantage due to the nature of the cam follower
means ensures that a sufficiently large magnitude force is
available to deflect or tilt the second housing 24 in the desired
direction, even when large loading resisting such movement are
applied.
It will be appreciated that a wide range of modifications and
alterations can be made to the arrangement described hereinbefore
without departing from the scope of the invention.
* * * * *